Coordinated Disclosure Timeline
- 2020-11-30: Issue reported to maintainers
- 2020-12-11: Report acknowledged
- 2021-02-28: Disclosure deadline reached
- 2021-03-01: Proposed to stretch the deadline for a week if the maintainers are actively working on the fix
Summary
The coverage-report.yml and generate-and-commit-files.yml GitHub workflows are vulnerable to unauthorized modification of the base repository or secrets exfiltration from a Pull Request.
Product
w3c/aria-practices GitHub repository
Tested Version
The latest changesets c4d8d14 and 24efd48 to the date.
Details
Issue: Untrusted code is explicitly checked out and run on a Pull Request from a fork
pull_request_target was introduced to allow triggered workflows to comment on PRs, label them, assign people, etc.. In order to make it possible the triggered action runner has read/write token for the base repository and the access to secrets. In order to prevent untrusted code from execution it runs in a context of the base repository.
By explicitly checking out and running build script from a fork the untrusted code is running in an environment that is able to push to the base repository and to access secrets.
on:
pull_request_target:
paths:
- "examples/**"
- "test/**"
- "!examples/landmarks/**"
...
steps:
- uses: actions/checkout@v2
with:
ref: refs/pull/${{ github.event.pull_request.number }}/head
- name: Install dependencies
run: npm ci
- name: Run coverage report
run: |
node test/util/report.js >> coverage.log || true
...
Impact
The vulnerability allows for unauthorized modification of the base repository and secrets exfiltration.
Credit
This issue was discovered and reported by GHSL team member @JarLob (Jaroslav Lobačevski).
Contact
You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2020-277 in any communication regarding this issue.